The present disclosure generally relates to tunable impedance load bearing structures, and more particularly, to active material based tunable impedance load bearing structures.
Load bearing structures such as beams, columns, rails, cables, panels, brackets, and the like are typically designed to withstand various static and dynamic external and internal forces and moments while maintaining their shape and position within acceptable deformation tolerances. A critical characteristic of these structural applications is stiffness. Currently, stiffness characteristics of a given load bearing structure can be improved by optimizing structure geometry and/or materials to suit certain loading conditions (e.g., foam filling hollow cross sections of a load bearing structure). For dynamic applications, the damping characteristics of the material may play a more critical role. In the case of a load bearing structure which is experiencing vibratory excitation, the damping properties of the structure may be optimized so that its performance excels when excited at a single frequency. The improved performance of these structures, however, is designed around a specific set of loading conditions. As such, the structure may not perform as desired under loading conditions outside the set of specific conditions focused on during design and fabrication of the structure.
Moreover, the specific characteristics desired at the time of manufacture and/or installation of the load bearing structure may actually be detrimental in certain situations, i.e., under circumstances where dramatically different load bearing characteristics would be advantageous. One example of such a situation, not intended to be limiting, could be in the automotive industry, where load bearing structures are designed to perform in a relatively rigid manner during normal operation, but during extraordinary circumstances, such as in an impact event, a drastically more compliant or a drastically stiffer structure may be preferable. Prior art load bearing structures are unable to make such significant changes in characteristics, rather these structures simply provide a fixed response, which is inherent to the characteristics contemplated at the time of design. In other words, current load bearing structures are not tunable.
Accordingly, there is a need for an improved load bearing structure. It would be desirable for such an improved load bearing structure to exhibit tunable impedance characteristics, i.e., be able to variously change structural and or material characteristics to meet changing load requirements in order to improve performance across a wider range of service conditions.